As discussed in more detail below, the COX enzyme is really two enzymes, COX-1 and COX-2, which serve different physiological and pathophysiological functions. As is well known, at antiinflammatory and/or analgesic doses, indomethacin, aspirin, and other NSAIDs effect great inhibition of COX-1, which protects the lining of the stomach from acid, along with relatively minimal inhibition of COX-2, which provokes inflammation in response to joint injury or a disease like arthritis. Also, certain NSAIDs possess essentially the same inhibitory activity against both COX-1 and COX-2. Thus, zeroing in on inhibition of COX-2 alone has been the goal of drug developers for several years in order to reduce or eliminate the GI irritation caused by COX-1 inhibition.
More specifically, as discussed in Smith, Garavito, and DeWitt, "D. L. Prostaglandin Endoperoxide H Synthases (Cyclooxygenases)-1 and -2", J. Biol. Chem., (1996) Vol. 271, pp. 33157-33160, the pertinent step in prostaglandin and thromboxane biosynthesis involves the conversion of arachidonic acid to PGH.sub.2, which is catalyzed by the sequential action of the COX and PER activities of PGHS, as set out in the following reaction scheme: ##STR1##
That COX activity originates from two distinct and independently regulated enzymes, termed COX-1 and COX-2, is described in DeWitt and Smith, "Primary Structure of Prostaglandin G/H Synthase from Sheep Vesicular Gland Determined from the Complementary DNA Sequence", Proc. Natl. Acad. Sci. U.S.A. (1988) Vol. 85, pp. 1412-1416; Yokoyama and Tanabe, "Cloning of Human Gene Encoding Prostaglandin Endoperoxide Synthase and Primary Structure of the Enzyme", Biochem. Biophys. Res. Commun. (1989) Vol. 165, pp. 888-894; and Hla and Neilson, "Human Cyclooxygenase-2-cDNA", Proc. Natl. Acad. Sci. U.S.A. (1992) Vol. 89, pp. 7384-7388.
COX-1 is the constitutive isoform and is mainly responsible for the synthesis of cytoprotective prostaglandin in the GI tract and for the synthesis of thromboxane, which triggers platelet aggregation in blood platelets. See, Allison, Howatson, Torrence, Lee, and Russell, "Gastrointestinal Damage Associated with the Use of Nonsteroidal Antiinflammatory Drugs", N. Engl. J. Med. (1992) Vol. 327, pp. 749-754.
On the other hand, COX-2 is inducible and short-lived. Its expression is stimulated in response to endotoxins, cytokines, and mitogens. See, Kujubu, Fletcher, Varnum, Lim, and Herschman, "TIS10, A Phorbol Ester Tumor Promoter Inducible mRNA from Swiss 3T3 Cells, Encodes a Novel Prostaglandin Synthase/Cyclooxygenase Homologue", J. Biol. Chem. (1991) Vol. 266, pp. 12866-12872; Lee, Soyoola, Chanmugam, Hart, Sun, Zhong, Liou, Simmons, and Hwang, "Selective Expression of Mitogen-Inducible Cyclooxygenase in Macrophages Stimulated with Lipopolysaccharide", J. Biol. Chem. (1992) Vol. 267, pp. 25934-25938; and O'Sullivan, Huggins, Jr., and Mccall, "Lipopolysaccharide-lnduced Expression of Prostaglandin H Synthase-2 in Aveolar Macrophages is Inhibited by Dexamethasone by not by Aspirin", Biochem. Biophys. Res. Commun. (1993) Vol.191, pp. 1294-1300.
Importantly, COX-2 plays a major role in prostaglandin biosynthesis in inflammatory cells (monocytes/macrophages) and in the central nervous system. See, Masferrer, Zweifel, Manning, Hauser, Leahy, Smith, Isakson, and Seibert, "Selective Inhibition of Inducible Cyclooxygenase-2 in vivo is Antiinflammatory and Nonulcerogenic", Proc. Natl. Acad. Sci. U.S.A. (1994) Vol. 91, pp. 3228-3232; Vane, Mitchell, Appleton, Tomlinson, Bishop-Bailey, Croxtall, and Willoughby, "Inducible Isoforms of Cyclooxygenase and Nitric Oxide Synthase in Inflammation", Proc. Natl. Acad. Sci. U.S.A. (1994) Vol. 91, pp. 2046-2050; Harada, Hatanaka, Saito, Majima, Ogino, Kawamura, Ohno, Yang, Katori, and Yamamoto, "Detection of Inducible Prostaglandin H Synthase-2 in Cells in the Exudate of Rat Carrageenin-Induced Pleurisy", Biomed. Res. (1994) Vol. 15, pp. 127-130; Katori, Harada, Hatanaka, Kawamura, Ohno, Aizawa, and Yamamoto, "Induction of Prostaglandin H Synthase-2 in Rat Carrageenin-Induced Pleurisy and Effect of a Selective COX-2 Inhibitor", Advances in Prostaglandin, Thromboxane, and Leukotriene Research (1995) Vol. 23, pp. 345-347; and Kennedy, Chan, Culp, and Cromlish, "Cloning and Expression of Rat Prostaglandin Endoperoxide Synthase (Cyclooxygenase-2) cDNA", Biochem. Biophys. Res. Commun. (1994) Vol. 197, pp. 494-500.
Hence, the differential tissue distribution of COX-1 and COX-2 provides a basis for the development of drugs that are selective COX-2 inhibitors (i.e., specificity for inhibition of COX-2 far exceeds inhibition of COX-1) as antiinflammatory, analgesic, and/or antipyretic agents with minimization of or without the GI and hematologic liabilities from COX-1 inhibition that plague most all currently marketed NSAIDs, most of which inhibit both COX-1 and COX-2, with specificity for COX-1 inhibition greatly exceeding that for COX-2 inhibition, although some have essentially similar inhibitory activity against both COX-1 and COX-2. See, for instance, Meade, Smith, and DeWitt, "Differential Inhibition of Prostaglandin Indoperoxide Synthase (Cyclooxygenase) Isozymes by Aspirin and Other Non-Steroidal Antiinflammatory Drugs", J. Boil. Chem. , (1993) Vol. 268, pp. 6610-6614.
Detailed SAR studies have been reported for two general structural classes of selective COX-2 inhibitors (specificity for COX-2 inhibition far exceeds COX-1 inhibition) including certain acidic sulfonamides and diarylheterocyclics. The in vivo activities of these selective COX-2 inhibitors validate the concept that selective COX-2 inhibition is antiinflammatory and nonulcerogenic, as discussed in the following journal articles. Gans, Galbraith, Roman, Haber, Kerr, Schmidt, Smith, Hewes, and Ackerman, "Anti-Inflammatory and Safety Profile of DuP 697, a Novel Orally Effective Prostaglandin Synthesis Inhibitor", J. Pharmacol. Exp. Ther. (1990) Vol. 254, pp. 180-187; Penning, Talley, Bertenshaw, Carter, Collins, Docter, Graneto, Lee, Malecha, Miyashiro, Rogers, Rogier, Yu, Anderson, Burton, Cogburn, Gregory, Koboldt, Perkins, Seibert, Veenhuizen, Zhang, and Isakson, "Synthesis and Biological Evaluation of the 1,5-Diarylpyrazole Class of Cyclooxygenase-2 Inhibitors: Identification of 4-[5-(4-Methylphenyl)-3 -(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide (SC-58635, Celecoxib)", J. Med. Chem. (1997) Vol. 40, pp.1347-1365; Khanna, Weier, Yu, Xu, Koszyk, Collins, Koboldt, Veenhuizen, Perkins, Casler, Masferrer, Zhang, Gregory, Seibert, and Isakson, "1,2-Diarylimidazoles as Potent Cyclooxygenase-2 Selective, and Orally Active Antiinflammatory Agents", J. Med. Chem. (1997) Vol. 40, pp. 1634-1647; Khanna, Weier, Yu, Collins, Miyashiro, Koboldt, Veenhuizen, Curie, Siebert, and Isakson, "1,2-Diarylpyrroles as Potent and Selective Inhibitors of Cyclooxygenase-2", J. Med. Chem. (1997) Vol. 40, pp. 1619-1633; Tsuji, Nakamura, Konishi, Tojo, Ochi, Senoh, and Matsuo, "Synthesis and Pharmacological Properties of 1,5-Diarylyrazoles and Related Derivatives", Chem. Pharm. Bull. (1997) Vol. 45, pp. 987-995; Riendeau, Percival, Boyce, Brideau, Charleson, Cromlish, Ethier, Evans, Falgueyret, Ford-Hutchinson, Gordon, Greig, Gresser, Guay, Kargman, Leger, Mancini, O'Neill, Quellet, Rodger, Therien, Wang, Webb, Wong, Xu, Young, Zamboni, Prasit, and Chan, "Biochemical and Pharmacological Profile of a Tetrasubstituted Furanone as a Highly Selective COX-2 Inhibitor", Br. J. Pharmacol. (1997) Vol. 121, pp.105-117; Roy, Leblanc, Ball, Brideau, Chan, Chauret, Cromlish, Ethier, Gauthier, Gordon, Greig, Guay, Kargman, Lau, O'Neill, Silva, Therien, Van Staden, Wong, Xu, and Prasit, "A New Series of Selective COX-2 Inhibitors: 5,6-Diarylthiazolo[3,2-b][1,2,4]-triazoles", Bioorg. Med. Chem. Lett. (1997) Vol. 7, pp. 57-62; Therien, Brideau, Chan, Cromlish, Gauthier, Gordon, Greig, Kargman, Lau, Leblanc, Li, O'Neill, Riendeau, Roy, Wang, Xu, and Prasit, "Synthesis and Biological Evaluation of 5,6-Diarylimidazo[2.1-b]thiazoles as Selective COX-2 Inhibitors", Bioorg. Med. Chem. Lett. (1997) Vol. 7, pp.47-52; Li, Norton, Reinhard, Anderson, Gregory, Isakson, Koboldt, Masferrer, Perkins, Seibert, Zhang, Zweifel, and Reitz, "Novel Terphenyls as Selective Cyclooxygenase-2 Inhibitors and Orally Active Anti-Inflammatory Agents", J. Med. Chem. (1996) Vol. 39, pp. 1846-1856; Li, Anderson, Burton, Cogburn, Collins, Garland, Gregory, Huang, lsakson, Koboldt, Logusch, Norton, Perkins, Reinhard, Seibert, Veenhuizen, Zhang, and Reitz, "1,2-Diarylcyclopentenes as Selective Cyclooxygenase-2 Inhibitors and Orally Active Anti-Inflammatory Agents", J. Med. Chem. (1995) Vol. 38, pp. 4570-4578; Reitz, Li, Norton, Reinhard, Huang, Penick, Collins, and Garland, "Novel 1,2-Diarylcyclopentenes are Selective Potent and Orally Active Cyclooxygenase Inhibitors", Med. Chem. Res. (1995) Vol. 5, pp. 351-363; Futaki, Yoshikawa, Hamasaka, Arai, Higuchi, lizuka, and Otomo, "NS-398, A Novel Nonsteroidal Antiinflammatory Drug with Potent Analgesic and Antipyretic Effects, which Causes Minimal Stomach Lesions", Gen. Phamacol. (1993) Vol. 24, pp. 105-110; Wiesenberg-Boetcher, Schweizer, Green, Muller, Maerki, and Pfeilschifter, "The Pharmacological Profile of CGP 28238, A Novel Highly Potent Anti-inflammatory Compound", Drugs Exptl Clin Res. (1989) Vol. XV, pp. 501-509; Futaki, Takahashi, Yokoyama, Arai, Higuchi, and Otomo, "NS-398, A New Anti-Inflammatory Agent, Selectively Inhibits Prostaglandin G/H Synthase/Cyclooxygenase (COX-2) Activity in vitro", Prostaglandins (1994) Vol. 47, pp. 55-59; Klein, Nusing, Pfeilschifter, and Ullrich, "Selective Inhibition of Cyclooxygenase-2", Biochem. Pharmacol. (1994) Vol. 48, pp. 1605-1610; Li, Black, Chan, Ford-Hutchinson, Gauthier, Gordon, Guay, Kargman, Lau, Mancini, Quimet, Roy, Vickers, Wong, Young, Zamboni, and Prasit, "Cyclooxygenase-2 Inhibitors. Synthesis and Pharmacological Activities of 5-Methanesulfonamido-1-indanone Derivatives", J. Med. Chem. (1995) Vol. 38, pp. 4897-8905; Prasit, Black, Chan, Ford-Hutchinson, Gauthier, Gordon, Guay, Kargman, Lau, Li, Mancini, Quimet, Roy, Tagari, Vickers, Wong, Young, and Zamboni, "L-745,337: A Selective Cyclooxygenase-2 Inhibitor", Med. Chem. Res. (1995) Vol. 5, pp. 364-374; Tanaka, Shimotori, Makino, Aikawa, Inaba, Yoshida, and Takano, "Pharmacological Studies of the New Antiinflammatory Agent 3-Formylamino-7-methylsulfonylamino-6-phenoxy-4H-1-benzopyran-4-one. 1st Communication: Antiinflammatory, Analgesic and Other Related Properties", Arzniem.-Forsch./Drug Res. (1992) Vol. 42, pp. 935-944; Nakamura, Tsuji, Konishi, Okumura, and Matsuo, "Studies on Anti-Inflammatory Agents. I. Synthesis and Pharmacological Properties of 2'-(phenylthio)methanesulfonamides and Related Derivatives", Chem. Pharm. Bull. (1993) Vol. 41, pp. 894-906; Chan, Boyce, Brideau, Ford-Hutchinson, Gordon, Guay, Hill, Li, Mancini, Penneton, Prasit, Rasori, Riendeau, Roy, Tagari, Vickers, Wong, and Rodger, "Pharmacology of a Selective Cyclooxygenase-2 Inhibitor, L-745,337: A Novel Nonsteroidal Anti-Inflammatory Agent with an Ulcerogenic Sparing Effect in Rat and Nonhuman Primate Stomach", J. Pharmacol. Exp. Ther. (1995) Vol. 274, pp. 1531-1537; and Graedon and Graedon, "Pills Promise Relief without Ulcers", The Raleigh, North Carolina News and Observer, p. 8D (Sep. 13, 1998) which addresses, in general terms, the development of celecoxib, meloxicam, and vioxx as selective COX-2 inhibitors.
Representative acidic sulfonamides and diarylheterocyclics that have been reported as selective COX-2 inhibitors in the journal articles mentioned in the above paragraph are: ##STR2## ##STR3##
Although acidic sulfonamides and diarylheterocyclics have been extensively studied as selective COX-2 inhibitors, there are very few reports on converting NSAIDs that are selective COX-1 inhibitors into selective COX-2 inhibitors. See, Black, Bayly, Belley, Chan, Charleson, Denis, Gauthier, Gordon, Guay, Kargman, Lau, Leblanc, Mancini, Quellet, Percival, Roy, Skorey, Tagari, Vickers, Wong, Xu, and Prasit, "From Indomethacin to a Selective COX-2 Inhibitor: Development of Indolalkanoic Acids as Potent and Selective Cyclooxygenase-2 Inhibitors", Bioorg. Med. Chem. Lett. (1996)Vol. 6, pp. 725-730; Luong, Miller, Barnett, Chow, Ramesha, and Browner, "Flexibility of the NSAID Binding Site in the Structure of Human Cyclooxygenase-2", Nature Structural Biol. (1996) Vol. 3, pp. 927-933; and Kalgutkar, Crews, Rowlinson, Garner, Seibert, and Marnett, "Aspirin-Like Molecules that Covalently Inactivate Cyclooxygenase-2", Science (1998) Vol. 280, pp. 1268-1270.
Also, interesting is U.S. Pat. No.5,681,964 (issued in 1997) to Ashton et al., assignors to the University of Kentucky Research Foundation, which shows conversion of indomethacin (an NSAID) into certain ester derivatives with concomitant reduction of GI irritation (see, FIG. 1 of U.S. Pat. No. 5,681,964 for the structure of the ester derivatives). Additionally, U.S. Pat. No. 5,607,966 (Parent)(issued in 1997) and U.S. Pat. No. 5,811,438 (CIP)(issued in 1998), both to Hellberg et al., assignors to Alcon Laboratories, show conversion of various NSAIDs (such as indomethacin) into certain ester derivatives and amide derivatives (which are useful as antioxidants and inhibitors of 5-lipoxygenase) but do not address COX-2 selective inhibition.
Moreover, although U.S. Pat. No. 3,285,908 (issued in 1966) and U.S. Pat. No. 3,336,194 (issued in 1967), both to Shen, assignor to Merck & Co., Inc., describe various secondary and tertiary amide derivatives of indomethacin, the patents fail to address COX inhibition, probably because COX inhibition (both COX-1 and COX-2) was undiscovered in the 1960's, and thus fail to recognize that tertiary amide derivatives do not inhibit either COX-1 or COX-2. (Also, see comparison compounds 9 and 10 in the Examples below.) However, U.S. Pat. No. 5,436,265 (issued in 1995) to Black et al. and U.S. Pat. No. 5,510,368 (issued in 1996) to Lau et al., both patents assigned to Merck Frosst Canada, Inc., describe, respectively, 1-aroyl-3-indolyl alkanoic acids and N-benzyl-3-indoleacetic acids as COX-2 selective inhibitors.
In the present investigation, the possibility has been explored for designing selective COX-2 inhibitors using as templates various compounds, such as NSAIDs, (1) that are selective COX-1 inhibitors or (2) that have essentially the same inhibitory activity for both COX-1 and COX-2. These two kinds of compounds are collectively referred to as compounds that are not selective COX-2 inhibitors.
More particularly, analysis of the human COX-2 crystal structure complexed with zomepirac-derived selective COX-2 inhibitors indicates that the structural basis for selectivity by zomepirac-derived compounds is different from that of diarylheterocyclics. See, Luong et al. mentioned above. Unlike diarylheterocyclics, zomepirac analogs do not utilize the side pocket; instead they breech the constriction at the mouth of the COX active site occupied by Argl06 and Tyr341 and project down the lobby region. The projection into this sterically uncongested region in the COX-2 active site opens the possibility that making a wide range of analogs of COOH-containing NSAIDs, each with a different pendent functional group replacing the OH of the COOH, would accomplish many purposes related to drug discovery or development. For example, certain pendent groups could improve water-solubility, bioavailability, or pharmacokinetics. Another possibility would be to attach a pendent pharmacophore in order to target a completely different protein leading to compounds with dual pharmacological functions.
Abbott Laboratories and Parke-Davis have attempted the pharmacophore approach. See, respectively, Kolasa, Brooks, Rodriques, Summers, Dellaria, Hulkower, Bouska, Bell, and Carter, "Nonsteroidal Anti-Inflammatory Drugs as Scaffolds for the Design of 5-Lipoxygenase Inhibitors", J. Med. Chem. (1997) Vol. 40, pp. 819-824; and Flynn, Capiris, Cetenko, Connor, Dyer, Kostlan, Niese, Schrier, and Sircar, "Nonsteroidal Antiinflammatory Drug Hydroxamic Acids. Dual Inhibitors of Both Cyclooxygenase and 5-Lipoxygenase", J. Med. Chem. (1990) Vol. 33, pp. 2070-2072. Both Kolasa et al. and Flynn et al. reported that replacement of the carboxylic acid group in NSAIDs with a hydroxamic acid moiety or a hydroxyurea moiety provided dual inhibitors of COX and 5-lipoxygenase. Nevertheless, none of the analogs displayed any significant selective COX-2 inhibition, and furthermore the hydroxamates underwent facile hydrolysis.
However, nothing in the above-discussed literature suggests that converting a COOH-containing drug, such as a COOH-containing NSAID, that is not selective for COX-2 inhibition into a derivative that is selective for COX-2 inhibition would also result in that derivative being a cancer inhibitor. Nevertheless, it is interesting to note that sulindac sulfide (an NSAID which contains a COOH moiety as well as a methyl sulfide moiety) is a 40-fold more potent inhibitor against COX-1 than COX-2, yet also exhibits inhibition of tumors. On the other hand, a derivative, namely sulindac sulfone (which contains a COOH moiety as well as a methyl sulfone moiety) does not inhibit either COX-1 or COX-2, but still exhibits inhibition of tumors.
Thus, it would be desirable to find certain COOH-containing drugs, such as COOH-containing NSAIDs, which are not selective COX-2 inhibitors (either display an inhibition for COX-1 far exceeding inhibition of COX-2 or display essentially the same inhibition for COX-1 and COX-2) that would, when converted into certain derivatives, become selective COX-2 inhibitors (display an inhibition for COX-2 far exceeding inhibition for COX-1), as well as retain the analgesic, antiinflammatory, and/orantipyretic effect of the drug, and yet exhibit other effects not exhibited by the drug prior to derivatization, such as cancer inhibition.